The present invention relates to a method for preparing a transparent electrode used for a display and, more particularly, to a method for fabricating an indium tin oxide film suitable for a transparent electrode for a display device such as a thin-film electroluminescent display panel.
The indium tin oxide (ITO) film comprises In.sub.2 O.sub.3 as the principal constituent containing SnO.sub.2. The ITO film is used as a transparent, conductive film because of its low resistivity and high transparency. It can be widely used as a transparent electrode for a thin-film electroluminescent display panel, a liquid crystal display, an electrochromic display cell, etc.
Recently, the ITO film has been fabricated by the following sputtering methods depending on the type of target as summarized in Table I.
TABLE I ______________________________________ Target Methods of Sputtering ______________________________________ Oxide (In.sub.2 O.sub.3 + SnO.sub.2) D.C. Sputtering " R.F. Sputtering Metal (In + Sn) D.C. Sputtering " R.F. Sputtering ______________________________________
Among these sputtering methods, reactive sputtering methods for applying a D.C. voltage in an atmosphere of active gases (Ar+O.sub.2) using the metal target are preferable considering the cost of the target and the apparatus. In particular, D.C. planar magnetron sputtering as the reactive sputtering is most preferable since it allows a wide selection of pressures by the sputtering gas, improves the sputtering rate, and is suited for straight-line deposition from the target to the substrate and, thus, for mass production.
However, disadvantageously, the D.C. sputtering methods using the metal target are poor in reproducibility of the ITO film. Therefore, it is desired to improve the reproducibility of the ITO film.